Rewards Question

I'm looking to book my honeymoon using miles. It would be:

EWR - MLE (stay for 7 days) - onward to HKT (7 days) - return to EWR

So:

EWR-MLE
MLE-HKT
HKT-EWR

I checked individual availability and see it, however when I do a mutti destination search once I select the EWR-MLE leg I receive the following message:

! We were not able to find any available flights for award travel meeting your requirements. You may modify your search criteria or review the MileagePlus Travel Award Rules. If you need additional assistance, call 1-800-UNITED-1 (1-800-864-8331) within the U.S. or Canada; elsewhere contact your local United Reservations Office.

I want to note that when I check individual flights such as EWR-MLE, MLE-HKT and HKT-EWR they have wide availability. So why would the search not allow this as there is wide availability? Help is appreciated!